The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel, to enable an expandable member to be substantially-freely expandable for filtering of the blood in the blood vessel or for occluding the blood vessel during the procedure. The system of the present invention is particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, such as the carotid arteries.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment of blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of an expandable member such as an expandable balloon in a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream which can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient""s vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, particles are not fully vaporized and enter the bloodstream. Likewise, not all of the emboli created during an atherectomy procedure may be drawn into the vacuum catheter and, as a result, the remaining emboli may enter the bloodstream as well.
When any of the above-described procedures are performed in the cerebral arteries, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Debris that is carried by the bloodstream to distal vessels supplying the brain can cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system following treatment utilizing any one of the above-identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient""s vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, often making such procedures in the carotid arteries a high-risk proposition.
Other techniques which have been developed to address the problem of removing embolic debris include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there have been complications with such systems since the vacuum catheter may not always remove all of the embolic material from the bloodstream, and a powerful suction could cause problems to the patient""s vasculature.
Further techniques which have had success include occluding of the blood vessel with an occluding balloon and perfusing the blood through a perfusion catheter past the occlusion, and the placement of a balloon filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. However, there have been problems associated with filtering and occluding systems, particularly during the expansion of the occluding balloon and balloon filter within the blood vessel. The portions of the balloon wall which are in contact in the unexpanded condition of the balloon may stick together, inhibiting the expansion and deployment of the balloon.
The above problems my arise from the expansion characteristics of the wall of the expandable balloon. The thickness of the wall of the expandable balloon may be substantially uniform, whereby the unexpanded in-contact portions of the balloon wall may tend to stick together and prevent deployment during expansion thereof, interfering the filtering of blood in the blood vessel or preventing the balloon from fully deploying within the vessel.
What has been needed is a reliable system and method for treating stenosis in blood vessels which enables the wall of the expandable balloon to be expandable, preventing portions thereof from sticking together during deployment and enabling full deployment of the balloon member in the area of treatment. The system and method should be relatively easy for a physician to use. Moreover, such a system should be relatively easy to deploy and remove from the patient""s vasculature. The inventions disclosed herein satisfy all of these and other needs.
The present invention provides a system and method for enabling an expandable balloon to be expandable in a blood vessel during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure, while preventing unexpanded in-contact portions thereof from sticking together during expansion and deployment of the expandable balloon. The present invention is particularly useful while performing an interventional procedure in vital arteries, such as the carotid arteries, in which critical downstream blood vessels can become blocked with embolic debris, including the main blood vessels leading to the brain or other vital organs. As a result, the present invention provides the physician with a higher degree of confidence that the expandable balloon will expand for occluding the blood vessel or for filtering the blood in the blood vessel thereby, and that the unexpanded in-contact portions of the expandable balloon will not stick together and inhibit deployment during expansion thereof.
The present invention enables an interventional procedure to be performed in a blood vessel at an interventional procedure site, such that the expandable balloon will expand and deploy for occluding or filtering thereby.
In the present invention, the system includes a catheter for positioning in a blood vessel at an interventional procedure site, an expandable member located in a distal end portion of the catheter for expanding and deploying in the blood vessel at the interventional procedure site, which includes a wall having an inner surface that includes portions thereof which are in contact in unexpanded condition, and an element for enabling the expandable balloon to be expandable.
In an embodiment of the present invention, the system includes a catheter, including an elongated shaft which includes a distal end portion adapted to be positioned in a blood vessel at an interventional procedure site. An expandable member, such as an expandable balloon, is adapted to be located in the distal end portion of the catheter shaft, and to be expanded and deployed in the blood vessel relative to the interventional procedure site, which expandable balloon includes a wall which includes a portion adapted to be fixed to the catheter shaft and a portion adapted to be expandable. The wall is adapted to be relatively stiff proximate the fixed portion thereof, and relatively flexible proximate the expandable portion thereof. The expandable balloon is in fluid communication with an inflation lumen. Upon inflation with a suitable fluid, the expandable balloon is expandable so as to be deployed within the blood vessel at the interventional procedure site, for occluding the blood vessel or for filtering the blood in the blood vessel. The expandable balloon enables deployment and prevents sticking together thereof upon expansion of the unexpanded in-contact portions.
In a particular embodiment of the present invention, the thickness of the wall of the expandable member is adapted to be substantially variable from the fixed portion to the expandable portion thereof, with the substantially variable thickness of the wall adapted to be substantially thick towards the fixed portion thereof, and substantially thin towards the expandable portion thereof The substantially variable thickness of the expandable balloon wall enables the expandable balloon to be expandable while exhibiting sticking together of portions thereof.
In another particular embodiment of the present invention, the expandable balloon further includes an enlarged portion located remote from the fixed portion thereof, for enhancing the ability of the expandable balloon to expand and deploy while preventing portions thereof from sticking together.
Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the invention, when taken in conjunction with the accompanying exemplary drawings.